I just recently connected with a 1st cousin and his mother who the family lost track of due to circumstances. My uncle divorced and met a woman who he fathered a child with. The day before said child was born my uncle died in an accident. The mother and her son stayed with my grandmother for almost a years time before leaving and that was the last I saw of them for 25+ years. I just reconnected through the power of the internet. When I was little we wondered if this woman would be our aunt. Does her being the mother of my 1st cousin make her my aunt? She is family regardless but my curiosity demands getting an answer to technically what her title would be.
English does not make any distinction between aunts and uncles by blood or by marriage. The spouses of your parents' siblings are your aunts and uncles, and that relationship does not cease upon the death of your blood relative. Thus the mother of your first cousin, your uncle's widow, is still your aunt. If she wishes to make a distinction between you and her siblings' children, however, she might introduce you as your late uncle's nephew.